Novel synergistic compositions

ABSTRACT

A method of controlling veterinary ectoparasites of mammals and birds of the sub-orders Ixodoidea and Sarcoptiformes comprising the application of a parasiticidally effective, non-toxic amount of a pyrethroid of formula ##STR1## together with at least one parasiticidal organophosphorus compound active against said ectoparasites.

This is a continuation of copending application Ser. No. 07/432,989 filed on Nov. 6, 1989, which is a division of U.S. Ser. No. 575,486, filed Jan. 31, 1984, now U.S. Pat. No. 4,897,386, which is a division of U.S. Ser. No. 391,455, filed June 23, 1982, now abandoned, which is a continuation of U.S. Ser. No. 863,738, filed Dec. 23, 1977, now abandoned.

This invention relates to novel potentiating compositions, their preparation, formulations containing them, the preparation of such formulations and to their use for the control of pests of the sub-Orders Ixodoidea and Sarcoptiformes.

Pyrethroids embraced by formula (I): ##STR2## are known from UK Patent No. 1,413,491 to possess insecticidal activity, and are known from South African Patent No. 3211/1975 to possess acaricidal activity.

Pests of the Class Insecta and of the Order Acarina are troublesome to man, animal and plants. They are vectors of disease, and economic losses result from their depredations on plants and animals. Control of such pests over the years has come to depend strongly upon the use of chemical pesticides which can be naturally occuring compounds or synthetic organic chemicals.

Organophosphorus pesticides are used in both the agricultural and veterinary fields with varying degrees of success. Some of these substances are common to both fields such as diazinon and malathion whilst others have been solely employed in the agricultural field, for example fenitrothion. In recent years resistance to organophosphorus compounds has evolved in certain strains of Insects and Acarids both of agricultural and veterinary importance and accordingly the need for new, effective insecticides and acaricides has arisen.

It is known from Japanese Patent Publication No. 058-237/1975, that potentiation of activity occurs between a pyrethroid of formula (I) and certain organophosphorus compounds against Insects and certain Mites of agricultural importance. Employing such potentiating compositions, renders the use of pyrethroids of formula (I) more economic. The Japanese publication also suggests that the potentiation is due to the interaction between the inhibition of the enzyme acetyl-cholinesterase by the organophosphorus compound at the ganglionic junctions of the pest, which results in ganglionic nerve paralysis, and the disturbance of axonal nerve transmittance through the cell membranes of the nerve axons of the pest by the pyrethroid, which results in impaired axonal nerve transmission.

It has now been surprinsingly found that there is potentiation between a pyrethroid of formula (I) and certain organophosphorus compounds against pests of veterinary importance which are resistant to conventional organophosphorus compounds and which belong to the sub-Orders Ixodoidea and Sarcoptiformes. It is believed that the potentiation is due to the inhibition by the organophosphorus compound of certain esterases which degrade pyrethroids. The various rates at which different groups of arthropod pests, even within the same Order of classification metabolise a pyrethroid makes it difficult to predict potentiation in one group of arthropod pests from a knowledge of potentiation in another group. This unpredictability is demonstrated by the absence of potentiation of insecticidal activity between a compound of formula (I) and an organophosphorus compound in respect of Insects of veterinary importance. (See Tables 6 to 9 below).

The pyrethroid for use in the present invention is selected from the esters embraced by formula (I) defined above. Structural formula (I) is intended to encompass all the possible geometric and optical isomers. More particularly the acid moiety of the ester may be selected from the (+)-cis-isomer, the (+)-trans-isomer, the (±)-cis-isomer, the (±)-trans-isomer and the (±)-cis-trans-isomer; the stereochemistry referring to that of the cyclopropane ring.

The preferred pyrethroid of this invention is 3-phenoxybenzyl-(±)-cis,trans-2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropane-1-carboxylate (permethrin).

The activity of these esters against pests of the sub-Orders Ixodoidea and Sarcoptiformes is potentiated when used in combination with at least one organophosphorus compound.

More particularly, the esters may be used in combination with phosphate and phosphorothioate compounds possessing intrinsic acaricidal activity. The organophosphorus compounds found to be effective are:

0,0-diethyl-0-(3-chloro-4-methyl-7-coumarinyl) phosphorothioate (coumaphos);

0,0-diethyl-0-(2,5-dichloro-4-bromophenyl) phosphorothioate (bromophos-Ethyl);

2,3-p-dioxanedithiol-S,S-bis, 0,0-diethyl phosphorodithioate (dioxathion),

0,0-diethyl-0-(3,5,6-trichloro-2-pyridyl) phosphorothioate (chlorpyrifos);

0,0,0',0'-tetraethyl, S,S'-methylenediphosphorodithioate (ethion);

3-(Dimethoxyphosphinyloxy)-N-dimethyl-ciscrotonamide (dicrotophos);

cis-1-methyl-2-(1-phenylethoxycarbonyl)vinylphosphate (crotoxyphos);

0-ethyl-0-(quinol-8-yl)phenylphosphorothioate (oxinothiophos);

(S-{5,7-dichlorobenzoxazol-2-yl-methyl}-0,0-diethyl phosphorodithioate) (benoxaphos);

S-[{(4-chlorophenyl)-thio]methyl}-0,0-diethyl phosphorodithioate (carbophenothion);

S-{(1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)-methyl}-0,0-dimethylphosphorodithioate (phosmet);

2-Chloro-1-(2,4-dichlorophenyl)vinyldiethylphosphate (chlorfenvinphos)

and a 1:1 weight by weight mixture of chlorofenvinphos and dioxathion.

Particularly high potentiation is achieved with combinations containing coumaphos, chlorfenvinphos, diazinon, ethion and the mixture of dioxathion and chlorfenvinphos.

The potentiating compositions of this invention are highly effective against strains of acarines which are susceptible to conventional organophosphorus acaricides as well as to those strains which are resistant to conventional organophosphorus acaricides such as Boophilus microplus (Can.) and B. decoloratus (Koch) and in addition those strains resistant to pyrethroids. The compositions of this invention may therefore be used to control acarine ectoparasites of animals, particularly those ticks of the genera Boophilus, Rhipicephalus, Amblyomma, Hyalomma, Ixodes, Haemaphysalis, Dermacentor, and Anocentor, and mites of veterinary importance for example the sheep scab mite Psoroptes ovis, and other ectoparasites of the sub-Orders Ixodoidea and Sarcoptiformes. Such ectoparasites infest stock and domestic animals and fowls, depending upon the location of the host and the particular ectoparasite. Common hosts are cattle, pigs, sheep, goats, horses, camels, chickens, dogs and cats.

The compositions of this invention may be used for protecting the host against infestations of Ixodid and Sarcoptic pests by application of the compositions themselves or in a diluted form in known fashion, as a dip, a spray, a dust, a paste, cream, gel, foam, shampoo or grease, a pressure-pack, an impregnated article, or a pour-on formulation. Dips are not applied per se, but the animals are immersed in a dipping bath containing the dip wash. Sprays may be applied by hand or by means of a spray race or arch or automatic treadle. Dusts may be distributed over the animals by means of a powder gun by hand application from suitable containers or incorporated in perforated bags attached to trees or rubbing bars. Pastes, foams, creams, gels, shampoos and greases may be applied manually or distributed over the surface of an inert material against which animals rub and transfer the material to their skins. Pour-on formulations are dispensed as a unit of liquid of small volume on to the backs of animals such that all or most of the liquid is retained on the animals.

The compositions may be presented either as formulations ready for use on the animals or as formulations requiring further dilution prior to application, but both types of formulations comprise a pyrethroid as defined above in combination with at least one organophosphorus compound as defined above in intimate admixture with one or more carriers or diluents. The carriers may be gaseous or solid or liquid or comprise mixtures of such substances and may be selected from one or more of the following:- a solvent, an inert carrier, wetting, stabilising, emulsifying, thickening, dispersing and surface active agents.

Dusts may be prepared by intimate admixture of the chosen compound with a powdered solid inert carrier for example suitable clays, kaolin, talcs, powdered chalk, calcium carbonate, Fuller's Earth, gypsum, diatomaceous earths and vegetable carriers.

Sprays of a composition of this invention may comprise a solution in an organic solvent (e.g. those listed below) or an emulsion in water (dip wash or spray wash) prepared in the field from an emulsifiable concentrate (otherwise known as a water miscible oil) or a water dispersible powder which may also be used for dipping purposes. The concentrate preferably comprises a mixture of the active ingredients, with or without an organic solvent and one or more emulsifiers. Solvents may be selected from kerosene, ketones, alkanols, xylene, aromatic naphtha, and other solvents known in the formulating art. The concentration of emulsifiers may be varied within wide limits and arc conveniently non-ionic or a mixture of non-ionic and anionic surfactants. The non-ionic surfactants will include polyoxyalkylene ethers of alkyl phenols, or of alcohols. The anionic compounds include salts of alkylaryl sulphonic acids.

Dip washes may be prepared not only from emulsifiable concentrates but also from wettable powders comprising a composition of this invention in intimate admixture with an inert carrier and one or more surface active agents, and possibly a stabiliser and/or an antioxidant.

Greases may be prepared from vegetable oils, synthetic esters of fatty acids or wool fat together with an inert base such as soft paraffin. A composition of this invention is preferably distributed uniformly through the mixture in solution or suspension. Greases may also be made from emulsifiable concentrates by diluting them with an ointment base.

Pastes are also semi-solid preparations in which a composition of this invention may be present as an uniform dispersion in a suitable base such as soft or liquid paraffin or made on a non-greasy basis with glycerin, mucilage or a suitable soap. As greases and pastes are usually applied without further dilution they should contain the appropriate percentage of the composition required for treatment.

Aerosol sprays may be prepared as a simple solution of the active ingredients in the aerosol propellant and a co-solvent such as halogenated alkanes and the solvents referred to above, respectively. Pour-on formulations may be made as a solution emulsion or suspension of a composition of this invention in a liquid medium which is of a viscosity such as to minimize loss of the formulation by run off from the surface of the animals. The pour-on formulation may be applied by a drenching gun, syringe or ladle or any other method known in the art.

A composition of the present invention preferably contains (5-95%) of a defined pyrethroid for example one selected from structural formula (I) and between (5-95%) of an organophosphorus compound defined hereinabove. The concentration of a composition applied to the pests or to their environment may be in the range of (0.0001-20%).

It will be appreciated from the foregoing that what we will claim may comprise any novel feature described herein, principally and not exclusively, for example:

(a) A novel composition comprising an ester of formula (I) in combination with at least one organophosphorus compound;

(b) A pesticidal formulation comprising a composition as defined in paragraph (a) together with a carrier therefor;

(c) A method of producing such a formulation; and

(d) A method of controlling veterinary ectoparasites of the sub-Orders Ixodoidea and Sarcoptiformes comprising the application to the ectoparasite or its environment, a composition or formulation as defined in paragraph (a) or (b).

The following Examples are provided by way of an illustration of the present invention and should not be construed as in any way constituting a limitation thereof.

EXAMPLE 1

Engorged female ticks of the Biarra strain of Boophilus microplus are immersed, in groups of 20 ticks per concentration, in a range of dilutions of the organophosphorus compound in combination with 3-phenoxybenzyl (±) cis, trans-2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropane-1-carboxylate (hereinafter referred to as Permethrin) at different ratios of organophosphorus compound to Permethrin.

The composite wash is prepared immediately prior to the test by dilution (with water) of the two constituents. The constituents may be in the form of miscible oil or wettable powder formulations. The desired range of concentrations for the test is obtained by further dilution of this master solution or wash.

The ticks are removed from the wash after 10 minutes, dried, and stuck dorsal side down on doublesided adhesive tape. They remain in this position for 14 days when the numbers laying viable eggs are determined. From this data a regression line is plotted (concentration against % inhibition of egg-production) and the IR90 and IR99 values determined (Table 1).

IR90=concentration at which 90% inhibition of egg-production occurs.

IR99=concentration at which 99% inhibition of egg-production occurs.

The values so obtained for the composite wash are compared with similar values obtained for the constituents of the composite wash when used alone. By reference to the equation for the harmonic mean, the factor of potentiation is determined (Table 2).

The equation for the harmonic mean is: ##EQU1##

The FOP figures for the IR99 values were calculated in the same way.

                                      TABLE 1                                      __________________________________________________________________________     IR90/99 Values for the Ixodicides alone and Compositions                       of those with Permethrin at various Ratios                                     PERMETHRIN                                                                              IXODICIDE                                                             COMPOSITE                                                                               ALONE  RATIO 1:1                                                                            RATIO 1:5                                                                              RATIO 5:1                                                                            RATIO 10:1                                                                            RATIO 20:1                          WITH     IR90                                                                               IR99                                                                              IR90                                                                              IR99                                                                              IR90                                                                              IR99 IR90                                                                              IR99                                                                              IR90                                                                               IR99                                                                              IR90                                                                               IR99                            __________________________________________________________________________     Coumaphos                                                                               1.0 -- 0.016                                                                             0.024                                                                             .0016                                                                             .0030                                                                               0.038                                                                             0.092                                         Composition A                                                                           0.75                                                                               2.6                                                                               0.011                                                                             0.017                                                                             .0031                                                                             .0053                                                                               0.060                                                                             0.15                                          Bromophos Ethyl                                                                         0.18                                                                               0.38                                                                              0.010                                                                             0.016                                                                             .0058                                                                             .0098                                                                               0.064                                                                             0.12                                          Diazinon 1.0 -- 0.095                                                                             0.21                                                                              .0030                                                                             .0056                                                                               0.017                                                                             0.038                                         Dioxathion                                                                              1.0 -- 0.016                                                                             0.038                                                                             .0028                                                                             0.023                                                                               0.044                                                                             0.060                                         Chlorpyrifos                                                                            0.085                                                                              0.24                                                                              0.008                                                                             0.014                                                                             .0046                                                                             .0062                                                                               0.020                                                                             0.024                                         Ethion   0.14                                                                               0.23                                                                              0.015                                                                             0.024                                                                             .0032                                                                             .0055                                                                               0.033                                                                             0.054                                         Dicrotophos                                                                             1.0 -- 0.063                                                                             0.15                                                                              .0080                                                                             0.016                                                                               0.044                                                                             0.094                                         Chlorfenvinphos                                                                         0.15                                                                               0.42                                                                              0.015                                                                             0.024                                                                             .0015                                                                             .0030                                                                               0.018                                                                             0.085                                                                             0.043                                                                              0.070                                                                             0.067                                                                              0.096                           __________________________________________________________________________      Composition A:A 1:1, weight by weight mixture of Chlorfenvinphos and           Dioxathion                                                                     Key: Ratio Ixodicide/Permethrin                                          

                                      TABLE 2                                      __________________________________________________________________________     Factors of Potentiation of composites of certain Ixodicides and                Permethrin                                                                     PERMETHRIN                                                                     COMPOSITE   RATIO 1:1                                                                             RATIO 1:5                                                                             RATIO 5:1                                                                              RATIO 10:1                                                                            RATIO 20:1                            WITH        IR90                                                                               IR99                                                                              IR90                                                                               IR99                                                                              IR90 IR99                                                                              IR90                                                                              IR99                                                                               IR90                                                                              IR99                               __________________________________________________________________________     COUMAPHOS   >3.9                                                                               -- >8.1                                                                               -- >1.8 --                                              COMPOSITION A                                                                              5.5 7.3                                                                               4.2 4.8                                                                                3.8 3.5                                             BROMOPHOS ETHYL                                                                            4.9 6.1                                                                               2.1 2.6                                                                                1.8 2.0                                             DIAZINON    >0.7                                                                               -- >4.5                                                                               -- >14.6                                                                               --                                              DIOXATHION  >3.9                                                                               -- >4.7                                                                               -- >5.6 --                                              CHLORPYRIFOS                                                                               4.6 6.0                                                                               2.5 3.8                                                                                3.4 7.3                                             ETHION      3.0 3.5                                                                               3.8 4.2                                                                                3.0 3.1                                             DICROTOPHOS >1.0                                                                               -- >1.6                                                                               -- >5.6 --                                              CHLORFENVINPHOS                                                                            3.1 4.1                                                                               8.1 8.1                                                                                5.7 3.0                                                                               2.8                                                                               4.6 2.0                                                                               3.8                                __________________________________________________________________________      Composition A:A 1:1, weight by weight mixture of Chlorfenvinphos and           Dioxanthion                                                                    Key: Ratio Ixodicide/Permethrin                                          

EXAMPLE 3 Miscible-Oil Formulations

    ______________________________________                                                   20:1   1:1     1:20                                                  ______________________________________                                         Dioxathion  20.0     10.5     1.0   pts. by wt.                                Permethrin   1.0     10.5    20.0   pts. by wt.                                Esso Solvent 200                                                                           59.0     54.0    49.0   pts. by wt.                                Ethylan KEO 20.0     20.0    20.0   pts. by wt.                                Cyclohexanone                                                                              --        5.0    10.0                                                          100.0    100.0   100.0                                             ______________________________________                                    

Ethylan KEO is an emulsifying agent which is a nonyl phenol ethoxylate condensate with an ethylene oxide average chain length of 9.5 mols, supplied by Lankro Chemicals Ltd.

Esso Solvent 200 is a mobile oil which consists of 95% of aromatic hydrocarbons.

EXAMPLE 4 Dusting Powder Formulations

    ______________________________________                                                 20:1    1:1     1:20                                                   ______________________________________                                         Coumaphos 0.01      0.10    0.20    pts. by wt.                                Permethrin                                                                               0.20      0.10    0.01    pts. by wt.                                Talc      99.79     99.8    99.79   pts. by wt.                                          100.0     100.0   100.0                                              ______________________________________                                    

EXAMPLE 5 Wettable Powder Formulations

    ______________________________________                                                       w/w         w/w     w/w                                          ______________________________________                                         Coumaphos     1.0%        15.0%   40.0%                                        Permethrin    20.0        15.0    2.0                                          Diatomaceous Earth                                                                           76.5        50.0    --                                           Kaolin        --          17.5    54.0                                         Dispersing Agent                                                                             2.0         2.0     3.0                                          Wetting Agent 0.5         0.5     1.0                                                        100.0       100.0   100.0                                        ______________________________________                                                            w/w     w/w                                                 ______________________________________                                         Ethion             2.0     25.0                                                Permethrin         20.0    1.5                                                 Diatomaceous Earth 60.5    36.0                                                Fullers Earth      15.0    35.0                                                Dispersing Agent   2.0     2.0                                                 Wetting Agent      0.5     0.5                                                                    100.0   100.0                                               ______________________________________                                    

EXAMPLE 6 Pressure-Pack Formulations.

In the following examples one of three pesticide mixtures may be used:

    ______________________________________                                         Mixture 1  Dioxathion     10    parts by weight                                           Chlorfenvinphos                                                                               10    parts by weight                                           Permethrin     1     part by weight                                 Mixture 2  Dioxathion     0.5   parts by weight                                           Chlorfenvinphos                                                                               0.5   parts by weight                                           Permethrin     1     part by weight                                 Mixture 3  Dioxathion     0.5   parts by weight                                           Chlorfenvinphos                                                                               0.5   parts by weight                                           Permethrin     20    parts by weight                                ______________________________________                                    

The above pesticide mixtures may be employed to formulate pressure packs containing between 0.0001% w/w and 20% w/w of each pesticide mixture as illustrated by the following examples:

EXAMPLE A

    ______________________________________                                         Pesticide mixture     0.0001% w/w                                              (either No. 1, 2 or 3 above)                                                   Odourless kerosene   10.0000% w/w                                              Methyl chloroform    29.9999% w/w                                              50/50 mixture of trichlorofluoromethane                                                             60.0000% w/w                                              and dichlorodifluoromethane                                                                         100.0000% w/w                                             ______________________________________                                    

EXAMPLE B

    ______________________________________                                         Pesticide mixture   20% w/w                                                    (either No. 1, 2 or 3 above)                                                   Methyl chloroform   50% w/w                                                    Dichlorodifluoromethane                                                                            30% w/w                                                                        100% w/w                                                   ______________________________________                                    

EXAMPLE 7

Highly tick susceptible cattle were placed in tick stalls and artificially infested with 0.25 g if B. microplus (Biarra strain) larvae before and after treatment. Twenty-four days after introduction the animals were divided into four groups and power-hand sprayed with 36 liters of wash per animal. The washes contained the following concentrations of active ingredients:

Group 1: 500 ppm Ethion

Group 2: 100 ppm permethrin

Group 3: 100 ppm permethrin and 500 ppm Ethion

Group 4: 50 ppm permethrin and 500 ppm Ethion

Engorged female ticks were collected daily from the washing baskets and counted. The results are illustrated in Table 5.

EXAMPLE 8

Engorged female ticks of the Biarra strain of B. microplus were immersed in serial ranges of concentrations of certain ixodicides alone. The ticks were then dried and stuck, dorsal side down, on double-sided sellotape. After 14 days the numbers of ticks laying viable egg batches were determined and the percentage plotted against concentration and a regression line drawn. The IR90/99 values were then determined as in Example 1. Having thus established the IR90/99 values for each of the chemicals under test equitoxic mixtures each comprising permethrin with one of the other ixodicides were prepared at the ratio of the IR99 values obtained. The master solutions were then diluted with water to the required range for the immersion test.

The results are illustrated in Table 10.

                  TABLE 5                                                          ______________________________________                                         DAILY TICK COUNTS                                                                                          Group 3                                                                        100 ppm Group 4 50                                 Time    Group 1   Group 2   permethrin                                                                             ppm perme-                                 in      Control 500                                                                              100 ppm   500 ppm thrin 500                                  Days    ppm Ethion                                                                               permethrin                                                                               Ethion  ppm Ethion                                 ______________________________________                                         -2          147       107     220     37                                       -1          148       126     520     122                                      Spray  0    220       79      270     180                                             1    148       31      3       3                                               2    176       17      1       1                                               3    432       41      0       3                                               4    490       13      0       9                                               5    235       27      0       7                                               6    258       51      0       0                                               7    233       38      0       0                                               8    187       71      0       0                                               9    265       17      0       0                                              10    289       86      0       73                                             11    245       32      0       10                                             12    500       12      0       17                                             13    300       10      0       17                                             14    285       27      0       19                                             15    300        7      0       10                                             16    250        4      0       10                                             17    230        0      0       9                                              18    200       14      0       6                                              19    110       12      0       2                                              20    360        0      0       0                                              21    700        0      0       0                                              22    420        0      0       1                                              23    220        0      0       0                                              24    220        4      0       0                                              25    490       21      0       0                                              26    1200      30      0       0                                              27    700       14      0       0                                              28    530       126     0       0                                              29    140       131     0       0                                              30    130       79      0       0                                              31     77       81      0       0                                              32    490       121     0       0                                              33    1450      130     4       1                                              34    780       178     27      38                                             35    1250      254     127     97                                       ______________________________________                                          Percentage control compared with Ethion treated group days 1-21 inclusive      No 2 100 ppm permethrin91.3%                                                   No 3 500 ppm ethion 100 ppm permethrin99.9%                                    No 4 500 ppm ethion 50 ppm permethrin96.8%                                     Protective period aginst larval reinfestation:                                 No 1 Nil                                                                       No 2 2 days                                                                    No 3 11 days                                                                   No 4 11 days                                                             

                                      TABLE 6                                      __________________________________________________________________________     LC50 values of individual organophosphorus insecticides and compositions       of these with                                                                  permethrin obtained both theoretically and by experiment against Musca         domestica                                                                      (CTB strain) (ratio 1:1)                                                                Experimental   Calculated                                                             LC50 Mixture  LC50 Mixture                                              LC50 Alone                                                                            as permethrin                                                                          LC50 Total                                                                           as permethrin                                                                          Factor of                                Compound (μg/♀)                                                                      (μg/♀)                                                                       (μg/♀)                                                                     (μg/♀)                                                                       Potentiation                             __________________________________________________________________________     Permethrin                                                                              0.027  --      --    --      --                                       Bromophos ethyl                                                                         0.102  0.029   0.043 0.021   0.74                                     Chlorpyrifos                                                                            0.094  0.025   0.042 0.021   0.84                                     Bromophos                                                                               0.114  0.021   0.043 0.022   1.02                                     Malathion                                                                               1.349  0.036   0.053 0.026   0.73                                     Diazinon 0.041  0.025   0.032 0.016   0.66                                     __________________________________________________________________________      LC50 is the minimum lethal dose expressed in μg required to kill 50% o      the flies                                                                

                                      TABLE 7                                      __________________________________________________________________________     LC95 values of individual organophosphorus insecticides and compositions       of these with                                                                  permethrin obtained both theoretically and by experiment against Musca         domestica                                                                      (CTB strain) (ratio 1:1)                                                                Experimental   Calculated                                                             LC95 Mixture  LC95 Mixture                                              LC95 Alone                                                                            as permethrin                                                                          LC95 Total                                                                           as permethrin                                                                          Factor of                                Compound (μg/♀)                                                                      (μg/♀)                                                                       (μg/♀)                                                                     (μg/♀)                                                                       Potentiation                             __________________________________________________________________________     Permethrin                                                                              0.054  --      --    --      --                                       Bromophos ethyl                                                                         0.170  0.097   0.082 0.041   0.43                                     Chlorpyrifos                                                                            0.161  0.083   0.081 0.041   0.49                                     Bromophos                                                                               0.241  0.063   0.088 0.044   0.70                                     Malathion                                                                               3.671  0.105   0.107 0.053   0.51                                     Diazinon 0.160  0.066   0.081 0.040   0.61                                     __________________________________________________________________________      LC95 is the minimum lethal dose expressed in μg required to kill 95% o      the flies                                                                

                                      TABLE 8                                      __________________________________________________________________________     LD50 values for individual organophosphorus insecticides and compositions      of these with                                                                  permethrin at various ratios against Musca domestica (Piggery II strain)                      Ratio 1:1       Ratio 1:10 (permethrin/OP)                                                                     Ratio 1:25                                                                     (permethrin/OP)                  Compound                                                                               LD50 (μg/♀)                                                                Calcu- lated                                                                        observed                                                                            ##STR3##                                                                             Calcu- lated                                                                        observed                                                                            ##STR4##                                                                             Calcu- lated                                                                        observed                                                                            ##STR5##              __________________________________________________________________________     Permethrin                                                                              0.235 --  --   --     --  --   --     --  --   --                     Dimethoate                                                                              0.179 0.20                                                                               0.20 1.0    0.18                                                                               0.13 1.4    --  --   --                     Diazinon 2.075 0.41                                                                               0.35 1.2    1.2 0.89 1.4    --  --   --                     Malathion                                                                               41.70 0.46                                                                               0.42 1.1    2.45                                                                               2.49 1.0    5.36                                                                               3.0  1.8                    Chlorpyrifos                                                                            2.171 0.41                                                                               0.38 1.1    1.25                                                                               0.76 1.7    --  --   --                     Bromophos ethyl                                                                         2.663 0.42                                                                               0.39 1.1    1.38                                                                               0.50 2.8    --  --   --                     Pirimiphos methyl                                                                       5.130 0.44                                                                               0.38 1.2    1.78                                                                               1.22 1.5    2.85                                                                               1.77 1.6                    __________________________________________________________________________      LD50 is the minimum lethal dose expressed in μg required to kill 50% o      the flies                                                                      OP = organophosphorus compound                                                 ##STR6##                                                                 

                                      TABLE 9                                      __________________________________________________________________________     LD95 values for individual organophosphorus insecticides and compositions      of these with                                                                  permethrin at various ratios against Musca domestica (Piggery II strain)                      Ratio 1:1       Ratio 1:10 (permethrin/OP)                                                                     Ratio 1:25                                                                     (permethrin/OP)                  Compound                                                                               LD95 (μg/♀)                                                                Calcu- lated                                                                        observed                                                                            ##STR7##                                                                             Calcu- lated                                                                        observed                                                                            ##STR8##                                                                             Calcu- lated                                                                        observed                                                                            ##STR9##              __________________________________________________________________________     Permethrin                                                                              0.63  --  --   --     --  --   --     --  --   --                     Dimethoate                                                                              0.66  0.65                                                                               0.53 1.2    0.66                                                                               0.62 1.1    --  --   --                     Diazinon 5.12  1.16                                                                               1.06 1.1    3.11                                                                               2.84 1.1    --  --   --                     Malathion                                                                               177.5 1.30                                                                               1.03 1.3    6.70                                                                               9.00 0.7    15.05                                                                              8.00 1.9                    Chlorpyrifos                                                                            10.66 1.23                                                                               0.85 1.5    4.36                                                                               1.79 2.4    --  --   --                     Bromophos ethyl                                                                         11.62 1.24                                                                               0.91 1.4    4.50                                                                               1.82 2.5    --  --   --                     Pirimiphos methyl                                                                       15.6  1.26                                                                               0.91 1.4    4.92                                                                               3.28 1.5     8.15                                                                              5.02 1.6                    __________________________________________________________________________      LD95 is the minimum lethal dose expressed in μg required to kill 95% o      the flies                                                                      OP = organophosphorus compound                                                 ##STR10##                                                                

                  TABLE 10                                                         ______________________________________                                         The activity of equitoxic mixtures of certain organo-                          phosphorus ixodicides with permethrin against viable                           oviposition of engorged female ticks of the Biarra                             strain of B. microplus                                                                     EQUITOXIC MIXTURE                                                  Permethrin        Expected  Actual  Factor of                                  Composite                                                                              ALONE     Value     Value   Potentiation                               with    IR90   IR99   IR90 IR99 IR90 IR99 IR90  IR99                           ______________________________________                                         Ethion  0.14   0.23   0.10 0.18 0.012                                                                               0.024                                                                               8.3   7.5                            Chlorfen-                                                                              0.15   0.42   0.11 0.28 0.025                                                                               0.059                                                                               4.4   4.7                            vinphos                                                                        Permethrin                                                                             0.066  0.13                                                            ______________________________________                                          ##STR11##                                                                      IR90 = concentration at which 90% inhibition of egg laying occurs              IR99 = concentration at which 99% inhibition of egg laying occurs        

EXAMPLE 9

    ______________________________________                                                           % w/w                                                        Aqueous Suspension Formulations                                                                    (a)     (b)     (c)                                        ______________________________________                                         Permethrin          1.0     8.0     20.0                                       Coumaphos           20.0    8.0     1.0                                        Sodium Dioctyl Sulphosuccinate                                                                     0.2     0.2     0.2                                        Xanthan Gum         0.3     0.4     0.3                                        Water               78.5    83.4    78.5                                                           100.0   100.0   100.0                                      ______________________________________                                    

EXAMPLE 10

    ______________________________________                                                        % w/w                                                           Diluent Free Formulations                                                                       (a)       (b)     (c)                                         ______________________________________                                         Permethrin       3.5       38.0    72.0                                        Diazinon         70.0      38.0    3.6                                         Epichlorhydrin   7.0       4.0     0.4                                         Ethylan KEO      19.5      20.0    24.0                                                         100.0     100.0   100.0                                       ______________________________________                                    

Ethylan KEO is an emulsifying agent which is a nonyl phenol ethoxylate condensate with an ethylene oxide average chain length of 9.5 mols, supplied by Lankro Chemicals Ltd.

REFERENCE EXAMPLE A

Mixtures of permethrin in combination with various organophosphorus compounds were prepared at 1:1, 1:10 and 1:25 ratios (ratio permethrin to organophosphorus compound). Solutions of the pesticides alone were similarly prepared.

The individual pesticides and the mixtures were diluted appropriately and applied by means of a microsyringe to the dorsal thorax of female CTB or Piggery II strain musca domestica flies. This topical application technique was performed on twenty females flies for each concentration of each mixture. The flies were then placed in a cardboard carton with access to sugar water for one day in order to assess mortality. Each concentration of each mixture was tested five times in a linked sequence over a period of several weeks.

The LC50 and LC95 value of each mixture was determined by means of probit analysis. A theoretical LC50 and LC95 value was calculated for each mixture by means of the equation of the harmonic mean.

The theoretical and experimental values were then compared in order to give factors of potentiation values.

The results are given in Tables 6 to 9, which indicate that little or no potentiation was observed. 

What we claim is:
 1. An acarcidal composition comprising an amount of a first compound permethrin and a second compound chlorpyrifos, the first and second compounds being present in an amount to provide a synergistic combination.
 2. A method of controlling veterinary ectoparasites of mammals and birds of the sub-orders Ixodoidea and Sarcoptiformes, which comprises the application of a parasiticidally effective amount, which is non-toxic to mammals or birds of the composition of claim
 1. 